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[en] Average neutron-induced reaction cross sections for ^134-138Ba (the barium isotopes of mass number 134 through 138) for incident energies between 20 keV and 20 MeV have been calculated by means of the optical and the statistical model with consideration of preequilibrium emission. The calculations comprise the total, the nonelastic, the differential elastic, and the (n,γ), (n,xnγ), (n,pγ), (n,pnγ), and (n,npγ) cross sections, as well as the production spectra of neutrons, protons, and gamma rays. For the model calculations, a consistent set of parameters based as much as possible on experimental data was employed. The computed cross sections are compared to available experimental results. Since such theoretical calculations are also of importance for nuclear data evaluation in cases where no experimental data exist, accuracy estimates of the predicted cross sections are given

[en] The g factor of 19/2^- state in ¹³⁹Ce has been measured by the method of the differential perturbed angular distribution of 1607-keV γ rays from the reaction ¹³⁷Ba(α,2n)¹³⁹Ce: g = +0.405(8). For the portion of the γ spectrum near 269 keV we have obtained the value gβ = 0.285(15) at T = 300 K, which presumably corresponds to the 10⁺ state in ¹⁴⁰Ce. The result for the 19/2^- state in ¹³⁹Ce agrees with the calculated value for the configuration (4⁺¹⁴⁰Ce x νh^-1/sub 11/2/ )(19/2^-)

[en] Continuing the systematic investigation into the photoexcitation of isomers over wide mass and energy ranges, the production of ⁷⁷Se^m, ⁷⁹Br^m, and ¹³⁷Ba^m was studied with the bremsstrahlung facility at the superconducting Darmstadt linear accelerator. These isomers have half-lives on the order of seconds. Excitation functions were measured for the (γ,γ') reactions populating the metastable states for energies of 2--7 MeV and the important intermediate states were identified. Nuclear structure calculations with the quasiparticle-phonon model for ⁷⁹Br and the particle- (hole-) core coupling approach for ¹³⁷Ba gave satisfactory descriptions for the strength and position of the dominant mediating levels. Admixtures of fragmented outershell single-particle strength shifted to low energies were identified as essential features of the wave functions of those states. Intermediate states in ⁷⁷Se displayed very large strengths compared to other isomers in the same mass region, providing further support for the correlation between integrated cross sections and ground state deformations recently discovered in the A=160--200 mass region. Such an enhancement would considerably improve the feasibility of a gamma-ray laser based on the sudden deexcitation of isomeric populations in deformed nuclei

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[en] The cross sections of the ¹³⁷Ba(n,p)¹³⁷Cs, ¹³⁶Ba(n,p)¹³⁶Cs, ¹³⁴Ba(n,p)¹³⁴Cs, ¹³²Ba(n,p) ¹³²Cs,¹³⁴Ba(n,2n)¹³³Ba and ¹³²Ba(n,2n)¹³¹Ba reactions have been measured by using the relative activation method. The standard cross sections of ⁵⁴Fe(n,p)⁵⁴Mn and ⁵⁴Fe(n,α)⁵¹Cr reactions at the neutron energy of 14.2 +- 0.1 MeV was used. The results obtained are compared with the data on hand

[en] The neutron capture cross sections of ¹³⁴Ba, ¹³⁵Ba, ¹³⁶Ba, and ¹³⁷Ba were measured in the energy range from 5 to 225 keV. Neutrons were produced via the ⁷Li (p,n)⁷ Be reaction by bombarding metallic Li targets with a pulsed proton beam. Capture events were registered with the Karlsruhe 4π barium fluoride detector. The cross section ratios were determined with an overall uncertainty of ∼3%, an improvement by factors of 5 to 8 compared to existing data. Severe discrepancies were found with respect to previous results. As a new possibility in time of flight experiments, isomeric cross section ratios could be determined for ¹³⁵Ba, ¹³⁶Ba, and ¹³⁷Ba. Maxwellian averaged neutron capture cross sections were calculated for thermal energies between kT=10 keV and 100 keV. These stellar cross sections were used in an s-process analysis. For the s-only isotopes ¹³⁴Ba and ¹³⁶Ba the N_s left-angle σ right-angle ratio was determined to 0.875±0.025. Hence, a significant branching of the s-process path at ¹³⁴Cs can be claimed for the first time, in contrast to predictions from the classical approach. This branching yields information on the s-process temperature, indicating values around T₈=2. The new cross sections are also important for the interpretation of barium isotopic anomalies, which were recently discovered in SiC grains of carbonaceous chondrite meteorites. Together with the results from previous experiments on tellurium and samarium, a general improvement of the N_s left-angle σ right-angle systematics in the mass range A=120--150 is achieved. This yields a more reliable separation of s- and r-process contributions for comparison with stellar observations, but reveals a 20% discrepancy with respect to the solar barium abundance

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